1. Field of the Invention
The present invention relates to a vehicle traction control device which is capable of preventing lowering of the traction or driving force available for the vehicle while controlling excessive slip in traction wheels or driving wheels of the vehicle, particularly at a low vehicle speed range.
2. Description of the Prior Art
In order to reduce the traction for the controlling of excessive slip in the traction or driving wheels, it has been known to make the combustion stroke of an engine ineffective, as shown, for example, in U.S. Pat. Nos. 4,432,430 and 4,589,511. In this case, low-select control is employed at a low vehicle speed range so as not to spoil the traction obtainable from reaction of a differential device. In said low-select control spinning of one of the traction wheels is permitted and when the other traction wheel also spins or slips excessively, the combustion stroke of engine is made ineffective.
In the above conventional measure, due to the fact that low-select control is carried out during low speed travel of the vehicle and an arrangement is required to prevent an engine stalling when its combustion stroke is made ineffective, the speed of that traction wheel which rotates faster than the other rises to an extremely high level in case of the traction control at a low vehicle speed. This may lead to a problem that the accelerating feeling is deteriorated and the traction is lowered.
Furthermore, if the engine has a plurality of cylinders, it may be considered that fuel supply to respective cylinders is cut in order to deactivate their combustion stroke. In this case, however, when the vehicle travels at a low speed and accordingly it takes a long time for the engine to perform one combustion cycle, the cycle of making fuel supply and cut of such fuel supply is prolonged thereby to cause judder of a suspension system. This undesirably results in lowering of the drivability.